There is more to going round the bend than meets the eye....

There are two types of corner the common tangential one, (i.e. part of a circle), or the progressive one, (which is more elliptical). The only one that is likely to be found on a layout that I build will be tangential... This makes the maths a lot easier!!!

The curves that I am using are 8 feet 9 inches radius -which gives a circumference of 55 feet. The gauge at the corners has to be larger than that for the straight sections to allow the wheelbase to move around it, (see HERE). The spread for Gauge ‘3’ track is 1mm -not a lot you might think -but remember that you have to ease the spread at the corners -both entering and leaving...

This leaves you with a slight problem... Yes it is only 1mm however you have to decide how you want to spread the track. Reading through the 1920's textbooks it seems there were two schools of thought on this.

The first dictates that: you spread the track evenly and allow the wheels to sit slightly lower as they enter the corner and this gives a smooth entry and exit to the corner at the expense of some wobble.

The second school of thought is that: you maintain the outer curve as a smooth tangent and spread the inner curve thus forcing the coning on the wheel to meet the corner with a smaller diameter and thus corner better.

The first school is the one I find the most "logical".

The second is the one that I feel is "right" -and this is the one that I will follow.

Another aspect that really has to be considered is that of Super Elevation -or banking up one side of the track, (the outer edge), to enable the train to take the corner at a higher speed. I have calculated the scale speed that most of my Gauge ‘3’ locos will be capable of, and a scale speed of 55kph does seem to be the most that they could ever do... But what is more important is the weight that the locos place on each rail. Proportionally speaking a model loco is far lighter than its real life image -thus has far less stability. Calculations show that the SE of the corners will have to start at 2mm and get to 4mm by the centre of the curve before returning to 2mm.

Well some two months of hammer and pin work later I am about to start making my first corner. Typically just on the market has arrived stainless steel rail, (by Cliff Barker), this is available in 1 and 2 yard lengths. Having built my jigs for 1 yard lengths this is going to be "fun".... Simple maths says that the number of yards required to make a 90 degree corner is 4 yards -or 2 by 2 yards lengths. This is of course highly appealing to me and I think that this is how I will progress. I am assured that the ABS fish plates provided by the Gauge 3 Society are quite robust enough for corners -but personally I would feel a lot happier with something rather more mechanically "meaty" and I have opted for "Hillmans Rail Clamps" to hold my corners together -I will only need 6 anyway...

The way I intend to construct my corners may seem rather bizarre -but there is a reason for it. I am going to construct sleepers with just chairs on one side (the outer) then position the sleepers radially to the centre. Next I am going to position the inner rail (with the chairs pre-fitted) and use my track gauge to position each inner chair 64.5mm from it. This will save me having to accurately bend a 2 yard length of rail to a radius of 8 feet 9 inches with the slow run in to the inner curve from 63.5mm to the spread corner gauge of 64.5mm.